The present invention relates to a sorter, and more specifically, it relates to a sorter which incorporates a stapler capable of stapling a stack of sheets.
A conventional copying machine may have a sorter for stacking the sheets from its image-developing process in a given order. One type of sorter includes a stapler for stapling each stack of sheets.
Japanese Patent Laying-Open No. 231757/1989 discloses one of the conventional sorters which has a stapler. The sorter has a plurality of bins for receiving sheets so as to sort them into a given order. The bins are disposed vertically and capable of moving vertically. A discharger is provided near the lowest end of the bins for the transport of sheets from a copying machine into the bins. A stapler for stapling the stacks of sheets stored in each bin is provided in the discharger.
In the conventional sorter, there is a predetermined gap between respective adjacent bins through which sheets are transported from the discharger into the bins. The stack of sheets stored in a bin is stapled by the stapler. The stapler can be rotated through a predetermined angle such that the stapler is located either in a drawn position, allowing the bins to pass, or in a stapling position, in which stapling operation is performed.
Japanese Patent Laying-Open No. 23154/1990 discloses another sorter which has a plurality of bins each of which is immovable. Sheets from a copying maching are transported by a transport mechanism which includes claws provided to correspond to the bins. In the sorter is a stapler which is vertically movable.
The stapling operation of the sorter is performed as follows: the stapler is moved vertically; a pincher draws the stack of sheets in a bin into a stapling position; the stapler staples the stack of sheets; and the pincher moves the stack back into the bin.
In the sorter disclosed in Japanese Patent Laying-Open No. 231757/1989, the stapler is disposed in the discharger, wherein the stapler is an obstruction to bins moving vertically. Consequently, a mechanism to rotate the stapler between the stapling position and the drawn position must be provided, complicating the structure. In the sorter disclosed in Japanese Patent Laying-Open No. 23154/1990, a device for drawing a stack of sheets out from a bin and moving the stack back into the pin must be provided in addition to the stapler, thus also complicates the structure of the sorter.
The above-described sorters, however, cannot accommodate any number of stacks of stapled sheets greater than the number of bins. Therefore, when a larger number of copies are to be produced, an operator must empty stapled sheets from the bins in order to allow succeeding sheets to pass into the bins. A plurality of sorters could be provided, in order to process a larger number of copies, but they would occupy a greater amount of space.
Japanese Patent Laying-Open No. 165270/1988 discloses a sorter consisting of a sorting portion and a stacking portion. When sheets are to be stapled by the sorter, stacks formed in the sorting portion are transported to the stacking portion, and then a stapler provided in the stacking portion staples the stacked sheets. Accordingly, the sorter can handle a number of copies larger than the number of bins provided in the sorting portion.
In the sorter, however, the stacks of sheets formed in the sorting portion become disarranged while they are transported toward the stacking portion, making it difficult to rearrange the stacks of sheets in the stacking portion before stapling.
Japanese Patent Laying-Open No. 179756/1985 discloses a sorter in which each bin is sloped, positioning the sheet-forward ends higher than the opposite ends, whereby stacks of stapled sheets can then be readily discharged into a storing portion. In the sorter, a sheet fed from the discharging portion of a copying machine automatically slides to a stop located at an end of each bin by its own weight. However, sheets of smaller size may easily stick in the middle of a bin. In such a case, the ends of all of the sheets cannot be arranged into adjustment, and the stapling operation cannot be performed satisfactorily. When the length of the sheets is much shorter than that of the bins, the leading edge of one sheet may knock against the trailing edge of the preceding sheet, or one sheet may be transported under the preceding sheet. This results in a stapling of inferior quality at times.